Users of a computer typically enter input using either a keyboard or a pointing device. The latter, which is of particular interest to the present invention, includes such well-known devices as mice, joy sticks, track balls, light pens, and the like.
The operation of "mice" is typical of pointing devices. Movement of a mouse, which is typically held in the user's hand, causes a position indicator (cursor) on a video display connected to the computer to move in relatively the same direction and magnitude. The mouse usually includes a pair of transducers which detect the movement of the mouse in two orthogonal directions; in turn, these motion signals are supplied to the computer. In addition, mice often include two or three keys which can be depressed for supplying additional signals to the computer, e.g., for selecting choices from a displayed menu.
There are two basic types of mice: mechanical and optical. Mechanical mice employ an inverted track ball or "rollerball" which is rolled across a desk or other planar surface by the user. Two rollers touching the ball record its movement along X and Y axes. As the rollers rotate, encoders make and break electrical contact and send corresponding electrical pulses that the computer can use to track movement. Alternatively, some mechanical mice forego the rollerball and instead employ two rollers which protrude from the bottom of the mouse to sense the X and Y directional movements directly. In either, case friction (mechanical) contact is made with a planar surface, with movement along that surface generating motion signals.
Optical mice, on the other hand, employ a special reflective mouse pad instead of a rollerball. An optical mouse has two LEDs that shine two light beams, one red and one infrared, onto the mouse pad. Reflected light beams re-enter the mouse through lenses which focuses the light onto photodetectors. As the mouse moves, the pad alternately absorbs and reflects light; blue lines on the pad absorb the red light while black lines absorb the infrared light. The photodetectors detect the "makes" and "breaks," which the mouse converts to signals for the computer.
An optomechanical mouse, a hybrid, employs both mechanical and optical means to detect movement. Like the mechanical mouse, the optomechanical mouse employs a rollerball. Instead of using electrical contacts, however, the optomechanical mouse uses two LED/photodetector pairs to detect movement along X and Y axes. As the roller rotates, the encoders alternately make and break light beams which shine between each LED/photodetector pair. Corresponding electric signals are sent to the computer to describe the motions of the mouse.
Regardless of the type, all of the foregoing mice generate motion signals by dragging a mouse device across a flat surface, such as a desk top. Commonly, a corresponding display cursor moves across the video display. Typically, though, the cursor tracks the relative movement of the mouse, not its absolute or physical movement. To allow the user to move the cursor with some precision, the ratio of mouse movement to cursor movement (mouse "sensitivity") is usually much less than one. In other words, a large mouse movement is mapped as a small cursor movement on the screen. This allows better fine motor manipulation of the cursor on the screen.
Occasionally, however, the user will want to move the cursor across a large screen distance, for example, from one side of the display to another. This is accomplished by "stroking" the mouse: repeatedly dragging the mouse across the desk top in a stroking fashion. In between each stroke (i.e., during back stroke), the mouse is lifted off the desk so that mechanical or optical contact is lost. Since no motion signals are generated during the reverse or back stroke, the cumulative effect is movement of the cursor in the stroke direction only.
In addition to the basic mouse design, a variety of other computer input designs are known. U.S. Patent No. 4,654,648, for example, describes a position control system having a wireless moveable "steering means" which emits acoustic signals, tracking means for receiving the acoustic signals and determining the position of the steering means by hyperbolic triangulation, and means for communicating the position of the steering means to a video display terminal. U.S. Pat. No. 4,578,674 describes a wireless cursor position device which operates by transmitting and receiving ultrasonic and infrared signals between the device and a control base. The control base includes an infrared emitter and at least two ultrasonic detectors; for three-dimensional (3-D) cursor control, additional ultrasonic detectors are required.
Cordless or wireless variants of input devices are known. U.S. Pat. No. 4,550,250, for example, describes a cordless input device which includes a pulse-driven light source whose duty cycle is controlled for conveying information. The detector has a housing with two spaced-apart optical slits for passing planes of infrared light onto concave light guides. The light guides, along with photoelectric sensors, produce positionally dependent, analog signals. The signals are processed by a microprocessor to determine the Cartesian coordinates of the device. U.S. Pat. No. 4,754,268 also describes a cordless input device. The cordless mouse indicates movement of the device on a planar surface by transmitting radiowaves to a host computer.
The keys of mouse devices have also been refined. U.S. Pat. No. 4,994,795, for example, describes a mouse input device having a plurality of programmable keys, with one embodiment including forty keys. A program controls the input device so that key signals are given priority. In the event that both key and motion signals occur, the key signals are supplied to the computer. If no key signal occurs, however, then motion signals are converted into key signals and are supplied to the computer.
While the prior art includes input devices having a variety of configurations (e.g., mouse, stylus, track ball, and the like) and means for communicating movement to a computer (including both cord and cordless models), the prior art input devices are largely confined to conveying two-dimensional (2-D) movement, i.e., movement along a planar surface. Of those systems which suggest a three-dimensional input device, the information conveyed to a computer is limited to positional information, i.e., the location of the device within an X, Y, and Z coordinate system.